中文摘要：

文件完整性验证是云存储服务的一项重要安全需求．研究者已经提出多项针对云存储文件完整性验证的机制，例如数据持有性验证（prove of data possession，PDP）或者数据可恢复证明（proof of retrievability，POR）机制．但是，现有方案只能够证明远程云存储持有一份正确的数据，不能检验其是否保存多份冗余存储．在云存储场景中，用户需要验证云存储确实持有一定副本数的正确文件，以防止部分文件意外损坏时无法通过正确的副本进行恢复．提出的多副本文件完整性验证方案，能够帮助用户确定服务器正确持有的文件副本数目，并能够定位出错的文件块位置，从而指导用户进行数据恢复．实验证明，充分利用了多服务器分布式计算的优势，在验证效率上优于单副本验证方案．

英文摘要：

Cloud storage services have quickly gained enormous popularity. They offer great convenience for data storage and sharing. However, since all user data are kept on remote servers and out of user＇s control, user may concern about data status. In order to expand storage service, data integrity verification is one of the critical security requirements for cloud storage service to fulfill. In order to verify the integrity status of files on remote cloud servers, many mechanisms have been proposed, such as PDP and POR. However, these methods can only ensure that the remote server holds ONE COPY of user data correctly. In fact, user needs to make sure that there are multiple copies kept on remote servers, incase that the corrupted file parts could not be recovered with a right copy. In this paper, we propose a multi-copy integrity checking scheme, which enables user to verify that HOW MANY COPIES are actually correct in the server. And this scheme could also identify the corrupted file blocks, thus to guide data recovery. Experimental results show that it has better performance comparing with the one copy schemes, owing to the distributing computations to multiple servers.